Deep-drawn Paper Tray Stepped Wall Wrinkle Prevention
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Solution Overview
Problem
Existing deep-drawn paper trays often suffer from wrinkling issues during the manufacturing process, leading to leaks in the sealed packages due to uneven surfaces, particularly at the corners and rim flanges, which compromise the air-tight and liquid-tight sealing.
Innovation Solution
A method and apparatus for deep-drawing paper trays that involve positioning a paper blank between upper and lower moulding tools, moving them to form a tray bottom and upwardly expanding side walls in multiple steps, creating a concentrically stepped profile to prevent wrinkling, with each step's height and width adjusted to accommodate the paper material without deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deep-drawing is performed in a single step, then manufacturing time is reduced, but the paper substrate wrinkles and tears during deformation
Solution Approach 1:
The deep-drawing process is divided into multiple sequential steps, where each step forms a portion of the side wall at a different height. The first step forms the lower portion, the second step forms the upper portion, and subsequent steps form additional portions, allowing controlled deformation at each stage without causing wrinkles or tears in the paper substrate.
Solution Approach 2:
Before completing the full deep-drawing operation, preliminary drawing steps are performed to gradually shape the side walls. Each preliminary step prepares the substrate for the next deformation stage by creating intermediate forms that reduce stress concentration and prevent material failure during the final drawing completion.
2Shape
If the side walls are formed with high curvature, then the tray depth is increased, but wrinkles appear on the surface
Solution Approach 1:
The side wall formation is segmented into multiple height portions, with each drawing step creating a specific curvature zone. By distributing the curvature across multiple controlled steps rather than applying it all at once, the paper substrate can adapt to the deformation gradually, maintaining surface smoothness while achieving the required tray depth.
3Strength
If the paperboard is made stiffer to maintain tray structure, then structural strength is improved, but the material becomes more prone to wrinkling during drawing
Solution Approach 1:
The multi-step drawing process includes preliminary deformation steps that gradually prepare the stiff paperboard for subsequent shaping. Each preliminary step introduces controlled deformation that progressively softens and adapts the material, allowing the stiff paperboard to be formed into deep trays without wrinkling while maintaining its structural strength in the final product.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively prevents wrinkling across the entire height of the tray side walls, ensuring a wrinkle-free, liquid- and gas-tight seal by allowing the paper to adapt to deformation without bending, thus enhancing the sealing integrity of the packages.
Implementation Method 1
moving the moulding tools in relation to each other, to form a tray bottom and at least one step of upwardly expanding side walls surrounding the bottom
Data Source
AI summary
A deep-drawn paper tray made of paper material, a method and an apparatus for manufacturing the tray, and a closed product package comprising the tray. The tray having a bottom and upwardly expanding side walls around the bottom, the side walls of the tray being shaped to expand through a plurality of circumferential steps dimensioned low enough for obtaining wrinkle-free side walls for the tray. The outermost step is a flat, wrinkle-free rim flange, which enables liquid and gas proof heat-sealing of a lid to form the package. The apparatus may comprise upper and lower moulding tools with concentric movable frames for forming the tray bottom and side wall steps from paper blanks, and moulding tools may be mounted onto a rotating turret carrying a paper blank through working stations arranged along the turret circumference, to shape the tray bottom and the side wall steps at the consecutive stations.